1. Field of the Invention
The present invention relates generally to a form of concentric tube drill pipe assembly and, more particularly, but not by way of limitation, it relates to improved drill pipe that enables wide variance in weight and buoyancy while containing space for continuous communication and electronic modules, such drill pipe being particularly adaptable for extended horizontal or deviated drilling applications.
2. Description of the Prior Art
Dual tube concentric drill pipe has been known for a long number of years as it has been utilized for obtaining various advantages in the drilling operation. An early U.S. Pat. No. 1,024,310 proposed a concentric drill pipe intended for boring shallow oil or artesian wells with reduced danger of blocking the hole as might be caused by breaking of the drill bit downhole. A U.S. Pat. No. 1,746,132 taught a concentric drill pipe wherein an annulus portion forms a sealed chamber for air or other gas which serves to lessen the weight of the drill stem.
A U.S. Pat. No. 3,928,903 teaches a specific form of construction for concentric drill pipe using only threaded interconnector means in the assembly. U.S. Pat. No. 4,280,535 teaches yet another form of concentric drill pipe that utilizes a more basic approach wherein a conventional form of drill pipe contains a smaller diameter pipe extending axially therethrough while being concentrically spaced by a number of spacer lugs. Finally, U.S. Pat. No. 3,265,091 is of interest for its teaching of concentric drill pipe that provides an annular space for carrying fluid or other material for the purpose of damping vibrations set up during drilling activity.
U.S. Pat. No. 4,560,012 in the name of McNeely provides teaching of a drill collar having inner and outer pipes with threaded pin and box ends securely affixed to the outer pipe. The inner pipe is aligned by abutment with an axial bore in the pin and box end joints, and the annular space is filled with a suitable foam plastic of selected specific gravity. This device is intended to function as a drill collar that has sufficient rigidity but lighter weight so that it is suitable for high angle deviation drilling or the like. This patent teaches mere capping or abutment of the inner tube with the opposite threaded inserts, a type of joinder that would not provide sufficient sealing capability.